There is a wide variety of protective enclosures in the marketplace. For example, it may be desirable to isolate the user from certain corrosive chemicals which he may have need to use. In such instance it is desirable to place a protective material surrounding those chemicals. In other cases it may be desirable to isolate the user from radioactive or toxic chemicals and a suitable enclosure is thus provided. Another type of enclosure available in the art is a protective or resilient type of enclosure surrounding a sensitive mechanism which can be easily damaged if dropped or roughly handled. The enclosure of the present invention differs from each of such devices and yet incorporates certain of the features noted above.
In the workplace the worker may be surrounded by atmospheric conditions conducive to danger. For example, an oxygen rich atmosphere might be particularly conducive to flash fire caused by a stray spark. A similar condition could exist in a dust laden atmosphere or in an atmosphere which includes flammable vapors.
In such hazardous environment, the worker may be required to operate such electrical equipment as meters, hand-held computers, calculators or the like. In such an environment, a stray spark can have calamitous consequences. Accordingly, it is desirable to enclose such meters or calculators within a protective enclosure which prevents such stray spark from igniting the atmosphere outside the protective enclosure. Therefore the protective enclosure must maintain a positive atmosphere around the enclosed device to prevent the outside atmosphere from leaking into the enclosure. The positive atmosphere can be said to purge the outside atmosphere from the enclosure. Moreover the protective or purge enclosure must provide means for monitoring the presence of a positive atmosphere within such protective enclosure. Moreover the positive atmosphere provided in the protective enclosure must not be so high as to restrict the operator in his use of the functions associated with the operating device enclosed therein, and/or the material used to form the enclosure must be sufficiently flexible to enable the user to operate the device contained within the enclosure without the loss of the positive atmosphere provided within such enclosure. Moreover the protective enclosure should include a positive visual indication that there is a positive atmosphere present in the protective enclosure. And the protective enclosure must be transparent to enable the user to see the device enclosed therein to effectively operate it. And the protective enclosure must be sealable to retain the positive atmosphere provided therein. And it is an important feature of the present invention that the protective enclosure be portable; that is, not joined to a hard line piping the protective atmosphere into the enclosure, and of lightweight construction, enabling the user to easily move the protective enclosure and the hand-held device encapsulated therein from location to location within the user's environment.